Referring to FIGS. 10-12, a tension-type telescopic support 60 includes an internal tube 62 in which a series of slots 64 is defined. The internal tube 62 can be inserted in an external tube 66. A frame 68 is installed on and around the external tube 66. The frame 68 includes two parallel fins 70 each formed with a cam 72. A restraining element 74 is installed on the fins 70. A locking element 76 is movably mounted on the fins 70. The locking element 76 includes two detents 78. A spring 80 is installed between the restraining element 74 and the locking element 76. A lever 82 includes a handle 84, two fins 86 extending from the handle 84 and two cams 88 each formed on one fin 86. The cams 88 are rotationally installed on the cams 72. A wheel 90 is rotationally installed on the cams 72. The wheel 90 includes a central gear 92 and two lateral gears 94 each formed on a side of the central gear 92. The central gear 92 is formed with teeth 96. Each lateral gear 94 is formed with ratchets 98 for engagement with the detents 78. A retaining element 100 includes a plate 102 at an end and a handle 104 at another end. The plate 102 is movably mounted on the fins 86. A spring 106 is provided between the retaining element 100 and the handle 84.
Referring to FIG. 11, one tooth 96 is inserted in one slot 64. The lever 82 is in a locking position. The detents 78 are engaged with the ratchets 98. The wheel 90 cannot be rotated counterclockwise. Thus, the internal tube 62 cannot be pulled from the external tube 66.
Referring to FIG. 12, one tooth 96 is inserted in one slot 64. The lever 82 is in a releasing position. The cams 88 push the locking element 76 so as to disengage the detents 78 from the ratchets 98. The wheel 90 can be rotated. Thus, the internal tube 62 can be pulled from or drawn back into the external tube 66.
This tension-type telescopic support is structurally complicated for using many elements. It is time-demanding to assemble this tension-type telescopic support. Every time the lever 82 is pivoted, the plate 102 contacts only one tooth 96. Thus, the wheel 90 is only rotated by an angle between two adjacent teeth 96. That is, the wheel 90 moves the internal tube 62 only by a distance between two slots 64. Therefore, it is slow to operate this tension-type telescopic support.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art.